1. Field of the Invention
The present invention relates to a broadband chip antenna, and more particularly to a super broadband chip antenna with first and second electrode patterns serving as radiation elements as well as a power-feeding element and a ground element, respectively.
2. Description of the Related Art
Recently, development trends of mobile communication terminals have been directed toward miniaturization and light weight. In order to satisfy these trends, internal circuits and components of the mobile communication terminal have been developed to be miniaturized. Therefore, an antenna of the mobile communication terminal has also been miniaturized. A planar inverted F-type antenna (referred to as a xe2x80x9cPIFAxe2x80x9d) is suitable for the miniaturization of the antenna of the mobile communication terminal, thus widely being used.
FIG. 1 shows a conventional chip antenna, i.e., a PIFA 10. With reference to FIG. 1, the PIFA 10 comprises a radiation patch 12 as a planar rectangular form, and a dielectric block 11. The dielectric block 11 includes a short-circuit pin 14 and a power-feeding pin 16. The short-circuit pin 14 and the power-feeding pin 16 are connected to the radiation patch 12. This configuration of the PIFA 10 is designed so that the radiation patch 12 is fed with a power via an electrical connection between the power-feeding pin 16 and the radiation patch 12 or an EM (Electro-Magnetic) feeding system, and a part of the radiation patch 12 is electrically connected to a ground portion (not shown), thereby being suitable for a resonant frequency or an impedance matching of the antenna 10. The PIFA 10 shown in FIG. 1 is operated by a system in which the current is induced on the radiation patch 12 with an electrical length to resonate at a designated frequency band range via the power-feeding pin 16.
However, this configuration of the PIFA has a problem of having a narrow frequency bandwidth.
FIG. 2 is a graph showing VSWR (Voltage Standing Wave Ratio) of the PIFA of FIG. 1. The narrow band characteristics of the PIFA of FIG. 1 are described with reference to the graph showing VSWR (Voltage Standing Wave Ratio) of the chip antenna for BT (Blue Tooth) band as shown in FIG. 2. As shown in FIG. 2, the PIFA for BT band has a bandwidth of approximately 180 MHz at frequency band of 2.34-2.52 GHZ with the VSWR of less than 2:1. This bandwidth seems to satisfy the BT band (approximately 2.4-2.48 GHZ), but actually it does not. That is, the actual frequency band of the antenna is changed by the form of the mobile communication terminal set employing the antenna. More particularly, the actual frequency band of the antenna is shifted by environmental influence acting on the mobile communication terminal such as a contact with a human body. As a result, it is difficult to have a usable frequency band satisfying a desired frequency band. The aforementioned narrow frequency band problem is an important drawback of a miniaturized chip antenna.
In order to solve the problem, in designing the chip antenna, the shifting of the resonant frequency and the impedance must be considered, thereby lengthening the development period and increasing the production cost of the chip antenna.
Further, in order to solve the narrowband characteristics, a distribution circuit such as a chip type LC device may be additionally connected to the antenna, thereby adjusting the impedance matching and obtaining a comparatively broad frequency band. However, this method of using an external circuit in adjusting the frequency of the antenna may cause another problem of deteriorating antenna efficiency. Alternatively, in order to obtain the broadband characteristics, the size of the antenna may be increased. However, since the increase of the size of the antenna does not satisfy the miniaturization trend, this method is not preferred.
Accordingly, a new PIFA structure, which satisfies the miniaturization trend, is usable at various frequency bands, and improves the narrow band characteristics, has been demanded.
Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a chip antenna comprising an electrode pattern formed on entire surfaces of a first surface, a second surface, and two opposite side surfaces disposed between the first and second surfaces of a dielectric block, and slits individually formed on the first and second surfaces, thereby dividing the electrode pattern into a first electrode pattern including a feeding port area and a second electrode pattern including a ground port area.
In accordance with one aspect of the present invention, the above and other objects can be accomplished by the provision of a chip antenna comprising: a dielectric block including a first surface, a second surface being opposite to the first surface, and side surfaces being disposed between the first and second surfaces; a first electrode pattern extending from a feeding port area formed on the first surface to the second surface via the adjacent side surface; and a second electrode pattern extending from a ground port area formed on the first surface to the second surface via the adjacent side surface, wherein a first slit is formed as an open area for connecting two opposite sides of the first surface so as to electrically separate the feeding port area of the first electrode pattern from the ground port area of the second electrode pattern, and a second slit is formed in the same direction as the first slit as another open area for connecting two opposite sides of the second surface so as to form an electromagnetic coupling between the first and second electrode patterns.
Preferably, the first and/or second electrode pattern(s) may extend so that a length of its one side adjacent to the first slit is substantially the same as a length of its the other side adjacent to the second slit.
Further, preferably, various tuning factors may be applied to adjust resonant frequency characteristics of the chip antenna. The resonant frequency characteristics of the chip antenna may be adjusted by varying an extending length L1 of the first electrode pattern and/or an extending length L2 of the second electrode pattern. Further, the resonant frequency characteristics of the chip antenna may be adjusted by varying a width of the second slit.
Yet, preferably, the chip antenna of the present invention may further comprise at least one supplementary slit formed on the first or second electrode pattern in order to separate the first or second electrode pattern into two electrode pattern areas. In this case, the resonant frequency characteristics of the chip antenna may be adjusted by varying a position and a form of the supplementary slit.
Still, preferably, at least one open area may be formed on the first or second surface. The resonant frequency characteristics of the chip antenna may be adjusted by forming the open area.
The first and second slits may be formed on the first and second surfaces so that the first electrode pattern extends from the feeding port area of the first surface to the second surface, and the second electrode pattern extends from the ground port area of the first surface to the second surface. Thus, the first and second electrode patterns may serve as radiation elements as well as a power-feeding element and a ground element, respectively. Since the power feeding and the radiation are successively achieved via the first and second slits, the chip antenna of the present invention has a much broader bandwidth.
In accordance with another aspect of the present invention, there is provided a chip antenna comprising: a dielectric block including a upper surface, a lower surface, and side surfaces being disposed between the upper and lower surfaces; an electrode formed on the entire surfaces of the upper and lower surface, and two opposite side surfaces; and slits for connecting opposite sides of two side surfaces without the electrode and dividing the electrode to a first electrode pattern and a second electrode pattern, each of the slits being formed on the upper and lower surfaces of the dielectric block, wherein the slit formed on the lower surface of the dielectric block at least separates a feeding port area from a ground port area, and the other slit formed on the upper surface of the dielectric block connects the first electrode pattern to the second electrode patterns by an EM(Electro-Magnetic) coupling.